174,240 research outputs found
The Discovery of Sgr A*
The compact radio source Sgr A* is associated with a 3.6 million black hole
at the center of the Milky Way. The radio source was discovered in February
1974 by Bruce Balick and Robert L.Brown. The National Radio Astronomy
Observatory's Green Bank 35 km radio link interferometer was used. We discuss
other observations in the years 1965-1985 as well as early VLBI observations.
The name Sgr A* was used for the first time in 1982 by Robert L.Brown and has
become the accepted name in the intervening years.Comment: 8 pages,2 figures. Conference proceedings: "The central 300 parsecs
of the Milky Way", editors A.Cotera, H.Falcke, T.R.Geballe, S.Markof
Afterthoughts | Complexities of Potency
Afterthoughts to themed perspectives on Complexities of Potency
Moduli of PT-semistable objects II
We generalise the techniques of semistable reduction for flat families of
sheaves to the setting of the derived category of coherent sheaves on
a smooth projective three-fold . Then we construct the moduli of
PT-semistable objects in as an Artin stack of finite type that is
universally closed. In the absence of strictly semistable objects, we construct
the moduli as a proper algebraic space of finite type.Comment: 34 pages. Exposition improved based on referee's comments, especially
the proofs of Prop 2.6 and 2.17 (of this version). References added; typos
corrected. Openness and separatedness now in a separate section. Sections 4
and 5 of previous version removed. Accepted for publication by the
Transactions of the American Mathematical Society. This is the sequel to
http://arxiv.org/abs/1011.568
A relation between higher-rank PT stable objects and quotients of coherent sheaves
On a smooth projective threefold, we construct an essentially surjective
functor from a category of two-term complexes to a category of
quotients of coherent sheaves, and describe the fibers of this functor. Under a
coprime assumption on rank and degree, the domain of coincides
with the category of higher-rank PT stable objects, which appear on one side of
Toda's higher-rank DT/PT correspondence formula. The codomain of
is the category of objects that appear on one side of another correspondence
formula by Gholampour-Kool, between the generating series of topological Euler
characteristics of two types of quot schemes.Comment: 19 page
China, the ‘East Asian Model’ and Late Development
There is an influential, neo-liberal proposition in the scholarly literature on China’s economic transformation since the late 1970s. It states that China’s reformed economic institutions are a mix of market-conforming and market-supplanting elements, that its developmental achievements so far have been ascribable to the conforming elements whereas the accumulated problems being ascribable to the supplanting elements, and that the problems have tended to outweigh the achievements as the country’s economic transition progresses from the allegedly easy phase to the difficult phase. This paper offers an alternative interpretation of the Chinese experience. The central proposition is that China’s economic institutions could be seen in favourable light both theoretically and with reference to the East Asian development experience. Specifically, the developmental implications of the market-conforming and market-supplanting elements should not be understood in any absolute sense, but rather depend on the appropriate match or otherwise between the institutions and the external environment. The developmental achievements to date indicate that China’s economic reform has managed to achieve a basically appropriate match between the two aspects, although enormous uncertainties still cloud over the future prospects owing to changes both in the external environment and the reform strategies of the state leadership
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